(b) Casualty Occurrence with respect to an Engine. Upon a Casualty Occurrence with respect to an Engine only, Lessee shall give Lessor prompt written notice thereof and shall, within sixty (60) days, but in no event later than ninety (90) days after the date of such Casualty Occurrence, convey to Lessor, as replacement for the Engine suffering a Casualty Occurrence, title to a Replacement Engine. Each Replacement Engine shall be free of all Liens (except those Liens which are permitted by Section 14 hereof), shall be the same or better make and model, and shall be in as good an operating condition as the Engine being replaced, assuming the Engine being replaced was in the condition and repair required by the terms hereof immediately prior to the Casualty Occurrence. Upon full compliance by Lessee with the terms of this paragraph, Lessor will transfer to Lessee title to the Engine which suffered the Casualty Occurrence. Prior to or at the time of any such conveyance, Lessee, at